title: Comparison of CaO's effect on the fate of heavy metals during thermal treatment of two typical types of MSWI fly ashes in China.
abstract: Both grate and fluidized bed incinerators are widely used for MSW incineration in China. CaO addition for removing hazardous emissions from MSWI flue gas changes the characteristics of fly ash and affects the thermal behavior of heavy metals when the ash is reheated. In the present work, two types of MSWI fly ashes, sampled from both grate and fluidized bed incinerators respectively, were thermal treated at 1023-1323 K and the fate of heavy metals was observed. The results show that both of the fly ashes were rich in Ca and Ca-compounds were the main alkaline matter which strongly affected the leaching behavior of heavy metals. Ca was mostly in the forms of Ca(OH)2 and CaCO3 in the fly ash from grate incinerator in which nascent fly ash particles were covered by Ca-compounds. In contrast, the content of Ca was lower in the fly ash from fluidized bed incinerator and Ca was mostly in the form of CaSO4. Chemical reactions among Ca-compounds caused particle agglomeration in thermal treated fly ash from grate incinerator, restraining the heavy metals volatilization. In thermal treated fly ash from fluidized bed incinerator, Ca was converted into aluminosilicates especially at 1323 K which enhanced heavy metals immobilization, decreasing their volatile fractions as well as leaching concentrations. Particle agglomeration hardly affected the leaching behavior of heavy metals. However, it suppressed the leachable-CaCrO4 formation and lowered Cr leaching concentration.
authors.affiliation: State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China.
authors.forename: Hong-Yun
authors.initials: HY
authors.lastname: Hu
authors.forename: Huan
authors.initials: H
authors.lastname: Liu
authors.forename: Wen-Qing
authors.initials: WQ
authors.lastname: Shen
authors.forename: Guang-Qian
authors.initials: GQ
authors.lastname: Luo
authors.forename: Ai-Jun
authors.initials: AJ
authors.lastname: Li
authors.forename: Zhao-Ling
authors.initials: ZL
authors.lastname: Lu
authors.forename: Hong
authors.initials: H
authors.lastname: Yao
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D017610:Calcium Compounds / Q000737:chemistry*; D060729:Coal Ash / Q000032:analysis*; D017745:Incineration / Q000379:methods*; D019216:Metals, Heavy / Q000032:analysis*; D010087:Oxides / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods; D014835:Volatilization
chemical_list: D000393:Air Pollutants; D017610:Calcium Compounds; D060729:Coal Ash; D019216:Metals, Heavy; D010087:Oxides; C016538:lime
keywords: CaO; Heavy metals; Leaching behavior; MSWI fly ash; Volatilization